The ideal thickness of a pond liner depends on the type of pond and the liner material. Keeping in mind that 1mm is equivalent to just under 40 mils. Keeping that in mind, 45 mil EPDM pond liners are the most popular choice. EPDM can also be found in 60 mil, which may provide extra durability for ponds with rocks and heavy plantings. However, 45 mil EPDM is already quite heavy and shipping costs can be prohibitive for even medium size ponds.
For RPE liners, which are inherently tougher thanks to their reinforced structure, a thickness of 20 to 30 mils is usually sufficient for residential ponds where significant wear from traffic, equipment, and exposure to harsh chemicals isn't expected. Using an underlayment can also reduce wear, allowing thinner liners to perform effectively without risking damage from underlying roots or rocks. In heavily trafficked or larger ponds, a thicker liner can offer added protection against all types of damage. For example, 60 mil RPE liners are reinforced with two layers of woven scrims for an extremely durable liner suitable for extremely challenging applications.
